Road tractors are generally used to pull trailers on roads to transport cargo. Aerodynamic apparatuses can be installed on the road tractor and/or on the trailer in order to reduce the aerodynamic air drag and improve fuel efficiency.
Rear drag-reducing apparatuses are generally installed and secured to a rear portion of a trailer to help manage the flow of air behind the trailer. It is known that a significant amount of air drag results when a vehicle travels over a roadway; this is due to an area of low pressure created at the rear end of the vehicle. For example, with a tractor-trailer type vehicle, the air makes a sharp bend around the squared-off back of the trailer, thus causing turbulence and drag. To overcome this problem, engine power is required and therefore fuel. Furthermore, the turbulence also causes poor visibility in rainy conditions and an accumulation of dirt on the back of trailers.
In the trucking industry, the aerodynamics of vehicles is a growing concern. Tests indicate that fuel savings from aerodynamic improvements are equivalent to fuel savings attained by a chassis weight reduction and require fewer services to maintain. The air resistance or aerodynamic drag of the vehicle increases the power needed by the engine as the speed increases. It is known that a tractor-trailer needs about 100 HP to overtake the air drag at a speed of 55 MPH. Approximately half the energy reaching the drive wheels is required to overcome air resistance at cruising speed. Recent tests reveal that the square back end contributes approximately to 30% of the air drag. Therefore, the addition of aerodynamic device, such as a rear deflector, diminishes the air drag and results in lower fuel consumption.
Various devices have been proposed to reduce air drag. One air drag reducing apparatus may be found described in U.S. Pat. No. 4,214,787 issued Jul. 29, 1980 to Chain wherein a pair of trim panels are pivotally connected to the rear end of the vehicle with control means connected between each trim panel and the rear end of the vehicle for maintaining the trim panel in an upward position when the vehicle is moving at a rate exceeding a predetermined minimum velocity. The drag reducing apparatus described in this patent includes a control assembly, which automatically controls the movement of the trim panels between an operating position and a storage position adjacent the vehicle doors. The control system comprises a panel actuator in the form of a ram, which is responsible to the application of pressurized fluid or air by the operator of the vehicle to maintain the panel in the drag reducing position. However, in this drag apparatus, the ram construction does not enable the doors to be moved between a closed position to a completely opened position where the doors are adjacently parallel to the sides of the trailer vehicle.
U.S. Pat. No. 6,485,087 teaches another air drag-reducing apparatus with foldable panels. The panels are manually operated and needs to be folded before opening the doors of the trailer prior to dock the trailer for adding or removing cargo therein.
Therefore, there exists a need in the art for an improved air drag reducing apparatus over the existing art. There is a need in the art for such an air drag reducing apparatus that can be easily expanded and collapsed. There is also a need for an air drag reducing apparatus that can be economically manufactured. There is also a need in the art for an improved air drag reducing apparatus that can be automatically expanded and collapsed. Moreover, there is also a need for an air drag reducing apparatus assembly that is appropriately sustaining vibrations caused by the vehicle circulating on the road.